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A U.S. news station debunks claims made by distributors of a plug-in 'energy-saving' device in December, 2007.
April 21, 2009
Beware of claims about
'power-saving' devices
Posted by Rob Klovance
“Wipe the smile off your electric company’s smug face! Instantly save electricity, legally and in less than five seconds!
- From an online ad for a black box, plug-in power saving component.
If only there were a wonder product you could plug in to the wall and instantly save 10, 15 or 30% on your electricity bill. The truth is that there’s no such product, despite some claims you’ll see online and, recently, via phone calls in British Columbia.
BC Hydro’s customer care department knows all too well the claims being made by those who manufacture or sell residential power quality conditioners, including the erroneous claim that BC Hydro Power Smart recommends or endorses them.
Related: Where to find current-sensing power bars, which actually do save energy
BC Hydro’s engineering department has spent a lot of time studying these devices, which are commonly referred to as “power savers.” Here’s their conclusion:
“These products can save extremely limited amounts of energy, and are therefore highly unlikely to be cost-effective in residential settings on the basis of energy savings alone. Power factor and power conditioning improve capacity and reliability (by providing protection against transient voltage spikes and harmonic currents), but do not necessarily save energy.”
If you want more technical details on how these products work and what they can actually save, read the technical explanation below. If you want to start saving by using proven, and in many cases free, tips and actions, join Team Power Smart and refer to our Green Your Home Guides & Tips sections.
About power quality conditioners
Residential power quality conditioners typically incorporate capacitors to improve power factor, filtering to reduce harmonic currents, and surge protective devices (SPDs, formerly known as transient voltage surge suppressors) to protect electronic equipment from transient voltages.
BC Hydro Power Smart is unaware of any physical mechanism by which these devices could cut residential energy consumption by even 1 or 2%, let alone the 10 to 20% savings (or more) that is sometimes claimed.
Several claims made by manufacturers of these devices are either misleading or incorrect. Here are a few examples, and our engineering department’s opinion on those claims:
Claim: By diverting transient voltage spikes, metal oxide varistors (MOVs) used in power quality conditioners will reduce the amount of energy that motors draw.
Fact: Although MOVs protect equipment from transient voltage spikes, they do not save energy.
Claim: These devices can "balance the voltage" by eliminating transient voltage spikes, thereby saving up to ten percent of energy consumption.
Fact: This is false for two reasons – unbalanced voltage can only occur in three-phase supplies, which aren't used in residential settings; and even in facilities with a three-phase supply, transient voltage spikes have an inconsequential impact on voltage balance. Data from the Institute of Electrical and Electronics Engineers demonstrates that even in the "noisiest" electrical environments, the cumulative time for transient voltage spikes amounts to less than 100 seconds per year. And in most facilities, the cumulative duration of transient voltage spikes is far less.
Claim: Capacitors in residential power quality conditioners make motors operate more efficiently by improving power factor.
Fact: Power factor is rarely an issue in a residential setting, but it is true that capacitors can improve power factor, and that doing so will save an extremely small amount of energy by reducing the reactive current that the upstream circuit must supply to a motor.
Rob Klovance is managing editor of bchydro.com.
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Source: BC Hydro
